A MULTI-RESOLUTION METHODOLOGY FOR THE 3D MODELING OF LARGE AND COMPLEX ARCHEOLOGICAL AREAS

A MULTI-RESOLUTION METHODOLOGY FOR THE 3D MODELING OF

LARGE AND COMPLEX ARCHEOLOGICAL AREAS

Gabriele Guidi1,*, Fabio Remondino2,3, Michele Russo1, Fabio Menna4, Alessandro Rizzi3, Sebastiano Ercoli1

1 Dept.INDACO, Politecnico of Milano, Italy – g.guidi@ieee.org, michele.russo@polimi.it, sebastiano.ercoli@polimi.it

2 Institute of Geodesy and Photogrammetry - ETH Zurich, Switzerland - fabior@ethz.ch

3 Centre for Scientific and Technological Research - Bruno Kessler Foundation, Trento, Italy - <remondino><rizziale>@fbk.eu

4 Dept. of Applied Sciences, Parthenope University, Naples, Italy - fabio.menna@uniparthenope.it

KEY WORDS: 3D modeling, multi-resolution, integration, image matching, laser scanning

ABSTRACT:

The article reports about a multi-resolution and multi-sensor approach developed for the accurate and detailed 3D modeling of the

entire Roman Forum in Pompei, Italy. The archaeological area, approximately 150 x 80 m, contains more than 350 finds spread all

over the forum as well as larger mural structures of previous buildings and temples. The interdisciplinary 3D modeling work consists

of a multi-scale image- and range-based digital documentation method developed to fulfill all the surveying and archaeological

needs and exploit all the intrinsic potentialities of the actual 3D modeling techniques. Data's resolution spans from few decimeters

down to few millimeters. The employed surveying methodologies have pros and cons which will be addressed and discussed. The

results of the integration of the different 3D data in seamlessly textured 3D model are finally presented and discussed.

1. INTRODUCTION

The generation of reality-based 3D models of objects and sites

is nowadays usually performed by means of images or active

sensors (like laser scanner or structured light projectors),

depending on the surface characteristics, required accuracy,

object dimensions and location, project's budget, etc. Active

sensors (Blais, 2004) provide directly 3D data and combined

with color information, either from the sensor itself or from a

digital camera, can capture relatively accurate geometric

details. Although still costly, usually bulky, with limited

flexibility, not easy to be use everywhere or at every time or

affected by surface properties, active sensors have reached a

maturity since some years and the range-based modeling

pipeline (Cignoni and Scopigno, 2008) is nowadays quite

straightforward although problems generally arise in case of

huge data sets.

On the other hand, image-based methods (Remondino and El-

Hakim, 200) require a mathematical formulation (perspective or

projective geometry) to transform two-dimensional image

measurements into 3D coordinates. Images contain all the

useful information to derive geometry and texture for a 3D

modeling application. But the reconstruction of detailed,

accurate and photo-realistic 3D models from images is still a

difficult task, particularly for large and complex sites or if

uncalibrated or widely separated images are used.

Besides range- and image-data, surveying information and

maps can also be combined for correct geo-referencing and

scaling.

Although many methodologies and sensors are available,

nowadays to achieve a good and realistic 3D model containing

the required level of detail, the best approach is still the

combination of different modeling techniques and sensors. In

fact, as a single technique is not yet able to give satisfactory

results in all situations, concerning high geometric accuracy,

portability, automation, photo-realism and low costs as well as

flexibility and efficiency, image and range data are generally

combined to fully exploit the intrinsic potentialities of each

approach (Guidi et al., 2003; Stumpfel et al., 2003; El-Hakim et

al., 2004; Guarnieri et al., 2006).

The continuously evolving and improving of sensor

technologies, data capture methodologies and multi-resolution

3D representation can contribute with an important support to

the refinement of information and to the growth of the

archaeological research. Furthermore there is an increasing

requests and needs for digital documentation of archaeological

sites at different scales and resolutions.

In this contribution we report our multi-resolution approach

developed for the reality-based 3D modeling of the entire

Roman Forum in Pompeii, Italy (Figure 1). The archaeological

area is approximately 150 x 80 m and contains more than 350

finds spread all over the Forum as well as larger structures of

previous buildings and temples. In this kind of projects,

adequate planning before the field work demands a systematic

approach to identify the proper sensor technology and data

capture methodology, estimate time for scanning and imaging,

define quality parameters, avoid tourists, etc. In the project, the

fieldwork had to be completed within a specific time dictated

by the availability of equipment and support personnel, allowed

access to the site and project budget. Thus, it was important to

assemble the right surveying methodology and an optimum

working team on the site to handle all operations effectively.

The modeling methodology was developed to fulfill all the

surveying and archaeological needs and exploit all the

potentialities of the actual 3D modeling techniques. The final

3D model will give to the Superintendence of Pompeii an

instrument to control the complex conservation of the site, to

educate and to provide to the common public a mean for

understanding the stratified Forum's structure.

\2. THE 3D MODELING PROJECT

The survey and 3D modeling of the Pompeii Forum is part of a

larger project regulated by two agreements among the company

ARCUS, the Archeological Superintendence of Pompeii (SAP)

and the Scuola Normale Superiore of Pisa. The first one

produced the new SAP Information System, for the

management of archaeological information (cataloguing

resources and geographic data) related to the vast area around

Mount Vesuvius. The second agreement, started in May 2007,

consists of (i) the generation of a website for the

communication to the broad public of studies and resources on

Pompeii's heritage and (ii) the developing of a 3D model of the

entire Forum. The modeling work is carried out by the

INDACO Department of the Politecnico of Milan in

collaboration with other scientific institutes and university

departments. The 3D modeling project is aimed at defining also

some best practices for data acquisition and rendering of 3D

models that will be realized in the future for the

Superintendence of Pompeii. The main objective is to establish

some core specifications for data acquisition and modeling, in

order to guarantee the scientific quality of data and the

interoperability of 3D models with the information System.

Thus, the working methodology is centered on the strict

cooperation between archaeologists and engineers. In addition

the final 3D results of the project will give to the local

superintendence an up-to-date, digital and three-dimensional

instrument for controlling the state of conservation of the

heritage, planning future preservation actions as well as

entertain the public with VR shows.

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